WAVES

Question 1

What is amplitude?

Answer 1

The maximum displacement from the equilibrium position.

Question 2

What is frequency?

Answer 2

The number of complete waves passing a point per second.

Question 3

What is wavelength?

Answer 3

The minimum distance between two in phase points on a wave on peaks/troughs

Question 4

What is phase difference?

Answer 4

The difference between the displacements of particles along a wave or on different waves

Question 5

What is time period?

Answer 5

the time it takes for a single point of the wave to undergo one whole oscillation

Question 6

Phase difference can be measured in….

Answer 6

radians, degrees/fractions of a cycle - one full wave = 2PI radians or 360 degrees

Question 7

What is polarisation?

Answer 7

Polarisation is a term used to describe the case when the oscillations of a transverse wave are restricted to a single plane. The process of polarisation is evidence for the nature of transverse waves, as longitudinal waves cannot be plane polarised, because their oscillations are restricted to one plane.

Question 8

Interference

Answer 8

the process of two coherent waves creating a resultant wave either through cancellation or reinforcement

Question 9

coherent

Answer 9

sources of waves are coherent if they emit waves of the same frequency with a constant phase difference

Question 10

path difference

Answer 10

Path difference is defined as: The difference in distance travelled by two waves from their sources to the point where they meet (at an interference fringe).
Path difference is generally expressed in multiples of wavelength

Question 11

What will white light interference produce?

Answer 11

a fringe pattern, however since white light is made up of a spectrum of different wavelengths, each fringe will be a spectrum of fringes varying in colour. Shorter wavelengths (blue) will be on the inner edge of each fringe, while longer wavelengths (red) will be on the outer edge.

Question 12

what is meant by diffraction

Answer 12

diffraction is the process of spreading out waves when passing through a gap or barrier.

Question 13

what is a diffraction grating

Answer 13

a screen with many thin slits
diffraction gratings are used to split white light into its visible colour spectrum

Question 14

There are several examples of stationary waves:

Answer 14

Stationary microwaves can be formed by reflecting a microwave beam at a metal plate, to
find the nodes and antinodes use a microwave probe.
● Stationary sound waves can be formed by placing a speaker at one end of a closed glass
tube, lay powder across the bottom of the tube, it will be shaken at the antinodes and settle
at the nodes. The distance between each node is half a wavelength, and the frequency of
the signal generator to the speaker is known so by c=fλ the speed of sound in air can be
found.

Question 15

Explain how polaroid sunglasses help to reduce the glare caused by reflections

Answer 15

They are polarised, which reduced the amount of waves that can get through (since only the waves that are aligned in the same direction can get through (only transmits vibrations in 1 direction).

Question 16

Why do you have to line up transmitting and receiving television aerials?

Answer 16

The rods of TV aerials are all horizontal because the receiving aerial must be lined up with the rods on the transmitting aerial, as they are polarised to be in the same direction. If they aren’t aligned, the strength will be lower.

Question 17

Explain why sound waves cannot be polarised (2 marks)

Answer 17

sound is a longitudinal wave
has vibrations in one plane only so cannot be polarised

Question 18

What is the principle of superposition?

Answer 18

The principle of superposition states that “When two or more waves with the the same frequency arrive at a point, the resultant displacement is the vector sum of the displacements of the wave.”

Question 19

What happens when a crest meets a slightly smaller trough?

Answer 19

Since they aren’t the same size, destructive interference is not total and not as noticeable, so the wave isn’t completely cancelled out, but the result is a smaller wave.

Question 20

How is polarisation used as evidence of the nature of transverse waves?

Answer 20

Polarisation can only occur if a wave’s oscillations are perpendicular to its direction of travel (as they are in transverse waves)

Question 21

How is polarisation used as evidence of the nature of transverse waves?

Answer 21

Polarisation can only occur if a wave’s oscillations are perpendicular to its direction of travel (as they are in transverse waves)